NASA always drops big news, but today was special. Seven Earth-sized exoplanets around a single star. Located 40 light-years away (that’s about 235 trillion miles), the seven planets are tucked in closely to their host star, TRAPPIST-1. Each planet orbits closer to its star than Mercury orbits our sun.
Planets close to a star isn’t usually a good thing. At least, when it comes to looking for the potential for life. Just look at Mercury. Nothing (that we know of) calls that scorched wasteland home. But TRAPPIST-1 isn’t like our sun. It’s much cooler and is known as an ultra-cool dwarf.
This system’s habitable zone, where liquid water can exist, is much different than our own. Because TRAPPIST-1 is much cooler, the zone where liquid water can exist is much closer to the star. Of the seven planets, three sit comfortably inside the star’s habitable zone. But NASA says all seven could be home to liquid water given the right conditions.
All seven of TRAPPIST-1’s planets. TRAPPIST-1e, f and g are the ones in orbiting in the habitable zone.
Take our own solar system for example. We know Earth has water. Scientists also believe liquid water exists on Jupiter’s moon Europa and Saturn’s moon Enceladus. While those moons are way outside the habitable zone, conditions around them make liquid water possible – mainly the gravitational effects of their nearby gas giants.
For the TRAPPIST-1 system, the planets outside of the habitable zone would need the right combination of atmospheric conditions for liquid water to form. But the best chance would be on the three planets at just the right orbits within the habitable zone.
What we know about TRAPPIST-1
TRAPPIST-1’s story begins in May 2016. Researchers using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) announced the discovery of three planets in the system.
With the help of several more ground-based telescopes and NASA’s Spitzer Space Telescope, researchers found TRAPPIST-1 was home to even more worlds. Spitzer’s data allows researchers to gather the first mass estimates for six of the worlds. After that, the density for each can be estimated and tells us six of them are likely rocky according to NASA. The mass of the seventh and farthest exoplanet hasn’t been estimated yet. Though, scientists believe it could be an icy world.
NASA also tapped the Hubble Space Telescope to help determine if the planets were gas or rocky. In May 2016, Hubble found there was no evidence for what the space agency calls “puffy, hydrogen-dominated atmospheres, typical for gaseous worlds like Neptune,” around the two innermost planets. That was good news for two reasons. It bolsters the case that the planets closest to the star are rocky. And, there isn’t a dense atmosphere smothering it.
“If they had a significant hydrogen-helium envelope, there is no chance that either one of them could potentially support life because the dense atmosphere would act like a greenhouse,” Nikole Lewis of the Space Telescope Science Institute explained last year.
Seven worlds. At least six of them believed to be rocky, and three orbiting the habitable zone. Scientists are understandably pumped.
“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,” said Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington. “Answering the question ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”
How do we get to the bottom of the ‘are we alone’ question? That’s where the next generation of telescopes come in. The James Webb Space Telescope is much more sensitive than the current set of telescopes. It will be able to detect the chemical signatures of these planets’ potential atmospheres. Water, methane, oxygen, ozone and more. It can even analyze a distant planet’s temperature and surface pressures.
“The TRAPPIST-1 system provides one of the best opportunities in the next decade to study the atmospheres around Earth-size planets,” Lewis said today.
The obstacles facing TRAPPIST-1’s planets
It isn’t as simple as being in the right orbit. One potential problem facing these planets is the fact they are all so close. Each one may be tidally locked to their star. That means the same side always faces the sun. Similar to how we see the same side of the moon all the time.
Tidally locked means one side of the planet in permanent sunlight while leaving the other in complete darkness. One side is hot, the other cold. The question is how hot? And how does a potential atmosphere spread out the temperatures? Extreme temperature swings are probably the norm on each one of these planets.
Another problem could be from X-ray and UV radiation. If the star is actively pumping out extreme radiation, the planets will need an ozone layer to protect it.
Despite the potential obstacles, TRAPPIST-1 will be a great target for future study. The Kepler space telescope is already busy taking a look at the system. That observation should wrap up in early March. With this data, researchers can refine their current data on the planets and see if they missed any. After that, we wait for the James Webb Space Telescope to take a peek at the system. That telescope is slated for launch next year.
What would it be like on one of these planets?
The view would be spectacular. Check out how the night sky would look from TRAPPIST-1d, one of the planet’s orbiting inside the habitable zone.
NASA also released a sweet travel brochure of what it would look like from TRAPPIST-1e.
C’mon Trump, give NASA a budget boost. Let’s turn sci-fi space travel into reality. Or, at least try.
Image credits: NASA